


Full Moon Rising

by hardbroken17



Series: Secrets of the Sea [1]
Category: Harry Potter - J. K. Rowling
Genre: Drama & Romance, Eventual Romance, F/F, F/M, Family Drama, Family Dynamics, Fluff and Angst, Harry wasn’t the only one with a scar from Voldemort, James Potter has a twin brother, Lily and James seen in flashbacks, Mermaid Reveal, Mermaid Transformation, Mermaids control all water, OCs are mermaids, Slow Burn, There was also a Girl Who Lived, Twin Drama, face scars, mermaid secrets
Language: English
Status: Completed
Published: 2021-01-27
Updated: 2021-01-27
Packaged: 2021-03-12 17:14:16
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,459
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29014161
Author URL: https://archiveofourown.org/users/hardbroken17/pseuds/hardbroken17
Summary: In the days nearing the end of the first Wizarding War, Twins were born of both worlds, bringing them together.Promises are made and broken, lives are taken, scars are made, power falls, as the Twins grow, to the chance to make their mark on the world.
Relationships: Harry Potter/Original Female Character(s)
Series: Secrets of the Sea [1]
Series URL: https://archiveofourown.org/series/2129634





	1. Full Moon

**Author's Note:**

> This has been in one of my old Harry Potter fanfic journals for a long time, and I thought that I’d write it here.
> 
> 😉

**Summary for the Chapter:**

> The Pierces have their five children and elemental powers are distributed to each of the children.

**Notes for the Chapter:**

> Enjoy

It was a cold, dark night in the North Sea, just off the coast of Scotland. The waves did not toss and turn, but remain bed still and quiet. When all of the sudden, ripples formed in the calm water, and a head came out. A mermaid broke the water’s surface, her silvery white hair soaked and stuck to her back. She looked around herself, making sure that she was alone before going back underwater, and a torpedo seemed to erupt under the water, where she had been. 

An island loomed over the sea, casting shadow and housing secrets that had remained untouched by human hands for thousands of years. On the west side of the island, was a tall volcano, and inside was where the full moon was focusing its light. 

The inside of the volcano was hollowed out and was extinct. The mermaid pod that had settled there had made sure that the volcano would never erupt and destroy the magical powers that the mermaids had had found that it had. The elderly mermaid came out of the water, running her hands over her face, and swam to the rocks, surrounding the cave, like a pool. 

”I wasn’t followed. We are safe. Katherina, my daughter, it is safe for you to begin the ritual.” The elder mermaid said, speaking to another of the two other merfolk in the cave. 

Katherina, nodded and pushed off of the rocks. 

”Yes Mother.” She said, and laid back, her long red hair floating around her head like waves, and her dark green tail floating on the surface of the cave pool, and her fully exposed chest, pale against the light that was shining down from the full moon. 

It was clear to see that Katherina was pregnant, and her belly was the only part of her figure, fully above the water. The elder mermaid held up her right hand and on her middle finger was a ring. It was made of silver and a bright blue stone, pale. 

The ring began to glow as the full moon passed directly over head the cave, shine down into the pool, on the pregnant mermaid, her mother, and a tan skinned merman with black hair, and a blue tail that matched his pale blue eyes. 

With a blinding flash, that filled the cave, and probably a few miles away, faint cries could be heard from the air. A loud splash filled the pool and Katherina called out. 

”Mother, Jason, they’re here.” She whispered, and her mother lowered her hand, the ring’s flow fading from the pool. 

”Oh Katherina, this is fate. Twins, oh!” She was cut off as the two female babies touched the seawater, and their tails appeared.

One was a shade of blue, dark fading to light, with pale skin, and cloudy grey eyes. 

The other couldn’t be more different from her sister. She had a green tail, but it was a different shade of green. Unlike her mother’s tail, this child had a tail that shone in all kinds of different shades of green. Her fins were already twitching, and her skin was tanned. She opened her eyes and looked at her mother, Katherina gazing down at her newborn daughter with love. 

Jason held out his hands to his wife and took the other twin, Katherina’s mother swimming to her daughter, and the heirs to the pod. 

”What are you going to name them my child?” She asked and Katherina smiled down at the girl in her arms, as the child batted her hands around. 

”Well, I think that my daughters should have roots in where they are from and who they come from, so I’m going to name you...Jacqueline.” Katherina decided and her mother smiled softly at the name, turning to Jason, holding the other baby. 

”Our daughters are the first ones of their kind. They deserve to be know as such, you my child, are...Diane-Jacqueline.” He said and Katherina’s mother opened her arms to the couple. 

”This has never happened before. Not just a mermaid marrying a human, but the birth of part mermaid, wizard, human children. To keep my granddaughters safe from the world outside, we must have a safe place for your family to stay until this is all over. Jacqueline and Diane-Jacqueline are the first children born of both worlds, earth and sea. And if there are two, there must be more on the way. Give the girls these when they are old enough to understand and they will learn of the world that they will have to run.” She said and handed Jason a closed clam shell.

”Thank you Dayana.” He said and Katherina kissed her mother on her cheek. The two children looked up at their parents, not knowing what their lives would become. 

—————

One Year Later

It had been a year since the birth of the Pierce Twins, Jacqueline and Diane-Jacqueline. Their grandmother, Dayana had used her aquatic powers on the manor that Jason’s mother had left him in her will. Ocean connecting tunnels were dug from a secret sea cave under the manor wove under land, and to the sea, where they could swim to Celesta Island. 

The Twins were a year old at thus point and their parents had just started letting Jason’s brother, James and his wife, Lily visit and see their nieces. The Pierce family hadn’t told James and Lily that they were all mermaids and couldn’t. Katherina had been talked by her husband into letting James and Lily babysit their guppies while Katherina’s next child was on the way, and was ready to come out on a full moon. 

James and Lily Potter arrived at the Pierce Manor, Jason hardly swapped pleasantries with his twin brother bride he handed James a sleepy Jackie and followed Katherina down to the sea cave, where the pair dove into the water and swam through the tunnels, to the ocean, and then, to Celesta Island. 

Katherina was not lifted into the air by the full moon’s glow this time. Instead, there was an unexpected problem with the full moon that night. The lunar eclipse crossed over and broke the magic, making Katherina splash back into the pool, but with a child in her arms when she emerged. 

Dayana looked at the child in shock, her hair was pitch black like her father’s, and she had no tail, only a pair of freckled legs. She was passed to her grandmother and the moment that the Moon Ring stone touched the child, the pool was filled with light and when the light cleared, a tail of silver and white was in place of the legs. Dayana tried to hand Katherina her child, but the tail vanished the second that the Moon Ring wasn’t touching her skin. 

Dayana looked around the pool and pulled a clam off of the edge of the rocks, holding it out to her daughter and Jason. 

”This is something I haven’t heard of in a long time. The eclipse being the birth of the child of the land above, while sustaining balance of the one below. She is the tru Yin and Yang my Katherina. She cannot transform without a Moon Ring. She has to always wear this, always and forever.” She said and Katherina took the clam, and opened it, with the Moon Ring inside. 

She took it out and slid it onto her child’s pointer finger. The silver and white tail reappeared and sparkled in the full moon’s light. 

”I think that I’ll name you...Kathleen.” Katherina said and smiled down at the girl, Kathleen looking up at her mom, with wide eyes. 

—————

Two Years Later

Jackie and DJ Pierce were spunky two year olds and were playing with each other, in their shared bedroom, until their dad came in, holding a one year old Kathleen on one arm. The child’s black hair was past her waist and pulled into a high bun. 

”Hey baby girls, Momma and I are going out to see your Nanna and in the meantime, Auntie Lily and Uncle James are going to visit, and they are bringing a special guest.” Jason said to his two year old, guppies, who jumped up and cheered about getting to see Uncle James and Auntie Lily. 

Jason heard the doorbell and before he could move, Jackie was at the door, throwing it open. 

”Uncle James!” She yelled and leapt into the awaiting arms of her uncle. James Potter squeezed his niece tightly, his glasses a little lopsided before he lowered an enthusiastic Jackie down, to be met by the more respectful and quiet twin, DJ. 

”Hi Uncle James.” DJ said and her uncle wrapped her up in a bear hug, putting her down, to help a pregnant Lily into the sitting room. Jason felt guilty about leaving his twin in the dark, but he knew that James would never understand what his life has been like when he had met Katherina. 

When he had gotten his brother set with Kathleen, Jackie, and DJ, Jason went down the hall, to the entrance to the sea cave. 

When he and Katherina got to the island, the moon was almost at its peak. Katherina was lifted up and everything moved almost the exact same way as it had when Jackie and DJ were born, only this time, there was a slight flaw in the moon magic. 

Jason held a little girl in his arms, her bright crimson and deep orange scales blended together perfectly with each other. Her skin was the same tone as Jackie’s and her eyes were different than her siblings. They were a stormy grey, and flecks of black. 

She was unique in the way that the other twin was not. He had a grey and black tail, and his eyes were closed. Katherina has a name for him almost immediately, while it took Jason some time to figure out one for the child that he was currently holding.

“I am going to call him Conner.” Katherina said as Jason looked over to his son. 

”This is Josephine.” He said and Dayana handed the couple the Moon Rings. When Katherina and Jason came back from the island, they came back up the sea cave, and through the secret passageway, and stairs down to the sea cave.

When they were above ground, the family rejoined and introduced Jackie, DJ, and Kathleen to their little brother and sister. James and Lily congratulated them and Sirius Black, James’ best friend since Hogwarts gave Jason a pat on the back. 

None of them could know what was going to happen to the Pierce and Potter families in only a year and a half.

**Notes for the Chapter:**

> This is the first part of the backstory of the Pierces, so that you know about the family history.


	2. Waning Spirits

**Summary for the Chapter:**

> Dumbledore suggests the Pierces join the Potters in hiding. 
> 
> Harry meets Jackie, Voldemort attacks and Jackie makes a huge sacrifice for her cousin.

**Notes for the Chapter:**

> This has been clouding my mind for so long and I have to get it out!!!

A year and a half had passed since Conner and Josephine (or Josie) Pierce has been born, and they were now both a year old. 

Their older siblings had aged also and were exited to meet their cousin Harry, in Godric’s Hollow. It had taken a lot of time for Dumbledore to allow them a safe passage to the Potter’s cottage, so that they could meet Harry. 

Of all of her siblings to change, Jackie was the one who changed the most. Her hair was strawberry blonde and cut to her shoulders. She and DJ were the oldest, four years old of only a week before they went to Godric’s Hollow, to meet Harry. 

When they were there, Jackie asked to see Harry. When Jackie held her cousin for the first time, it made her feel so great, and that she loved the feel of Harry’s skin. 

Jackie had been aware of her mermaid powers since Josie and Conner showed up and even though she had never questioned why Nanna never left the sea pool when she came to visit. Being a mermaid all her life had made her realize her powers a little early, and so she did, on Harry. 

While the family was in the lower level of the cottage, Jackie would manipulate orbs of water into shapes for Harry to laugh at. She was in the middle of doing a twirl in midair when her Uncle James came into the bedroom and saw them, Jackie instantly dropping the water back into the glass that was on the nightstand table. 

”I’m sorry Uncle James, I thought that you knew.” She said and her uncle merely picked her up and held her in a bear hug. 

”It’s not your fault Jackie. If Harry like it then it wasn’t hurting him, but I do need to talk to your mum and dad about this ok?” He asked and Jackie nodded, watching her uncle leave the room, an infant Harry in his arms.

Jackie had never been the kind of person who would sit by and not listen, constantly breaking the rules that her parents had set in place for her, DJ, Kathleen, Josie, and Conner’s safety. She would sneak into the grotto where her mum and dad would talk to eacc other about their guppies. She loved to sneak into the sea cave and get in, her iridescent green tail floating in the water and playing with the closed clam shell, engraved in runes, her name and DJ’s, wanting to know what was inside. 

She snuck down the stairs and right as she was about to tiptoe into the open, Jackie closed her hand in a soft fist, and became invisible. She went to the side of the couch, where Josie and Conner were fast asleep and her parents were sitting, talking to her Uncle James and her Auntie Lily. 

”So your wife is a mermaid turned into a human, and your children are mermaid human hybrids? And you can turn into a merman from human form?” James asked Jason, and his brother nodded, holding Katherina’s hand, his wife fiddling with the hem of the sweater she was wearing. Her red hair was braided up, around her head like a crown with shells in it. 

”Yes. I met Katherina when we were in our fifth year, and it was O.W.L week. We started talking and one thing lead to another and I fell in love with her. We married at sea and I was given the ability to become a merman, and Katherina gained legs.” Jason said and James nodded his head as Lily held Harry in her arms. 

”So the time that you asked us to babysit and Jackie, DJ, and then came back with Kathleen, I’m guessing that she was born at sea?” Lily asked and Katherina nodded her head. 

“Yes. The same thing with Josephine and Conner too. All our children were born at sea.” She said and James nodded his head. 

”And Jackie has magical powers over water?” James asked and Katherina sighed. 

”We are a different species of mermaid and all of our children are destined to have complete control over all forms of water if they put their minds to it. Jackie is the only one who is reckless and uses hers outside of home, and in the sea grotto.” She said and James raised his eyebrows.

”What’s a sea grotto?” He asked and Jason began to explain.

”It’s the sanctuary for us. We use it to connect to the ocean. We made sea tunnels that go underground and to the channels of the sea. Jackie likes to go inside and practice her powers on the pool inside.” He said and James nodded, just as there was a soft knock on the cottage door. 

Jackie ran back upstairs, and crouched down, at the top of the stairs as her aunt went it open the door. The young mermaid swept a lock of strawberry blonde hair out of her eyes as she watched her aunt. The door swung open and Lily smiled. 

”Dumbledore. Welcome, come on in.” She said and stepped back. Jackie peeked down and saw an old man wearing dark purple robes and a midnight blue traveling cloak. He had silver hair and a beard that was so long, he tucked it into his belt. A pair of half moon glasses were perched on his crooked nose. He smiled at Jason and Katherina when he saw them, and shook hands with James as he sat on an armchair. 

”Always a treat to see you Katherina. Jason. It is actually good that you and your family are here. I have been working and I think that it would be best for you and your family to go into hiding also Jason. A cottage right next to here has been all prepped for you and is ready for you to go to.” He said and Jason looked from his old headmaster, to his wife, brother, sister-in-law, nephew, and children. 

”When to we move in?” He asked and Dumbledore smiled softly. This was when Jackie came down the steps and the old man saw her. 

”So this is your oldest is that right Jason?” Dumbledore asked and Jason shook his head before Jackie spoke to Dumbledore.

”No, DJ is older by a few seconds. But I have a green tail.” She said as Dumbledore reached down and picked up the four year old. She giggled and snuggled into his robes. 

”She is a powerful one Jason. I know she will have a key in ending this war.” He said softly as Jackie played with the edge of his beard. 

The Pierces went into hiding, in a cottage beside the Potters. Jackie missed Harry but couldn’t leave the house, because of the charms keeping them hidden. Fall came and before they knew it, it was Halloween. 

Jackie watched all of the Muggle children run around and go candy hunting while she had to stay in her house, with no contact to the outside world. She had a glass of water next to her on the window seat and was circling her hands around an orb of it. 

She looked out the window and saw a black cloaked figure. It was walking slowly like a snake towards Auntie Lily and Uncle James’s house. She lowered the orb back to the glass and looked back out the window. The figure opened the front gate to the Potter house and walked in. Jackie thought that the gate was supposed to be closed and nobody could see the house. She got scared and went to tell her Daddy about it when she heard a loud crash, and Jason Pierce was out the door in a second. 

Jackie had no idea why she did it, but she ran into her uncle’s house after her dad. Jason let out a strangled croak, in the doorway as he saw his brother James, laying on the bottom two steps, dead, his glasses askew. 

Jackie became invisible and ran up the stairs. A cloaked figure was standing in the bedroom, raising a hand at her aunt. The skin of the person was white and he was holding a wand. 

Jackie hardly caught what he was saying to her aunt as she snuck around and behind her aunt, and stood by Harry’s crib. 

”Stand aside girl!” The man hissed, and Jackie got a glimpse of him. His skin was pale and white. His eyes were red pupils with slits, like a cat. He had a snakelike face and slits for nostrils.

”Please not Harry! Kill me and not Harry!” Her Auntie Lily screamed and the man chuckled an evil chuckle.

”Very well then.” He said and waved his wand, and Jackie heard the words leave his mouth before she saw a green flash of light. 

”AVADA KEDAVRA!” 

Her Auntie Lily fell to the floor and the man smiled evilly. Jackie was in shock and became visible again.

”So you must be that cousin. A pity I have to take your life too.” He said and Jackie watched him look at Harry. He raised his wand and Jackie leapt into the crib, holding her cousin.

”AVADA KEDAVRA!” 

Jackie felt a great amount of pain on her cheek and neck as the green light flashed. She opened her eyes and saw the man was gone and his wand clattered to the floor. 

She looked at Harry, who had a scar cut, shaped like a bolt of lightning across his forehead of untidy hair. She reached out to touch it as her father came in, and saw her. 

”Jacqueline, are you alright? Where did he go?” Her father asked and Jackie held up her arms, as Jason picked her up. She saw her Auntie Lily dead on the floor and buried her face into her dad’s chest only before her face hurt.

”Daddy, it hurts.” She said and Jason looked at her cheek.

”What hurts-oh my goodness.” He said as Jackie passed out. 

**Notes for the Chapter:**

> This is the last chapter until we start with the progressive story. To me, backstory is important


End file.
